Metal–organic frameworks (MOFs) have attracted tremendous interest due to their promising applications including electrocatalysis originating from their unique structural features. However, it remains a challenge to directly use MOFs for oxygen electrocatalysis because it is quite difficult to manipulate their dimension, composition, and morphology of the MOFs with abundant active sites. Here, a facile ambient temperature synthesis of unique NiCoFe‐based trimetallic MOF nanostructures with foam‐like architecture is reported, which exhibit extraordinary oxygen evolution reaction (OER) activity as directly used catalyst in alkaline condition. Specifically, the (Ni2Co1)0.925Fe0.075‐MOF‐NF delivers a minimum overpotential of 257 mV to reach the current density of 10 mA cm−2 with a small Tafel slope of 41.3 mV dec−1 and exhibits high durability after long‐term testing. More importantly, the deciphering of the possible origination of the high activity is performed through the characterization of the intermediates during the OER process, where the electrochemically transformed metal hydroxides and oxyhydroxides are confirmed as the active species.

Electrochemical water splitting for H2 production is limited by the sluggish anode oxygen evolution reaction (OER), thus using hydrazine oxidation reaction (HzOR) to replace OER has received great attention. Here we report the hierarchical porous nanosheet arrays with abundant Ni3N‐Co3N heterointerfaces on Ni foam with superior hydrogen evolution reaction (HER) and HzOR activity, realizing working potentials of −43 and −88 mV for 10 mA cm−2, respectively, and achieving an industry‐level 1000 mA cm−2 at 200 mV for HzOR. The two‐electrode overall hydrazine splitting (OHzS) electrolyzer requires the cell voltages of 0.071 and 0.76 V for 10 and 400 mA cm−2, respectively. The H2 production powered by a direct hydrazine fuel cell (DHzFC) and a commercial solar cell are investigated to inspire future practical applications. DFT calculations decipher that heterointerfaces simultaneously optimize the hydrogen adsorption free energy (ΔGH*) and promote the hydrazine dehydrogenation kinetics. This work provides a rationale for advanced bifunctional electrocatalysts, and propels the practical energy‐saving H2 generation techniques.

Replacing sluggish oxygen evolution reaction (OER) with hydrazine oxidation reaction (HzOR) to produce hydrogen has been considered as a more energy-efficient strategy than water splitting. However, the relatively high cell voltage in two-electrode system and the required external electric power hinder its scalable applications, especially in mobile devices. Herein, we report a bifunctional P, W co-doped Co 3 N nanowire array electrode with remarkable catalytic activity towards both HzOR (−55 mV at 10 mA cm −2) and hydrogen evolution reaction (HER, −41 mV at 10 mA cm −2). Inspiringly, a record low cell voltage of 28 mV is required to achieve 10 mA cm −2 in two-electrode system. DFT calculations decipher that the doping optimized H* adsorption/desorption and dehydrogenation kinetics could be the underlying mechanism. Importantly, a self-powered H 2 production system by integrating a direct hydrazine fuel cell with a hydrazine splitting electrolyzer can achieve a decent rate of 1.25 mmol h −1 at room temperature.

Hydrazine oxidation assisted water electrolysis offers a unique rationale for energy-saving hydrogen production, yet the lack of effective non-noble-metal bifunctional catalysts is still a grand challenge at the current stage. Here, the Mo doped Ni 3 N and Ni heterostructure porous nanosheets grow on Ni foam (denoted as MoNi 3 N/Ni/NF) are successfully constructed, featuring simultaneous interface engineering and chemical substitution, which endow the outstanding bifunctional electrocatalytic performances toward both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER), demanding a working potential of −0.3 mV to reach 10 mA cm −2 for HzOR and −45 mV for that of HER. Impressively, the overall hydrazine splitting (OHzS) system requires an ultralow cell voltage of 55 mV to deliver 10 mA cm −2 with remarkable long-term durability. Moreover, as a proof-of-concept, economical H 2 production systems utilizing OHzS unit powered by a waste AAA battery, a commercial solar cell, and a homemade direct hydrazine fuel cell (DHzFC) are investigated to inspire future practical applications. The density functional theory calculations demonstrate that the synergy of Mo substitution and abundant Ni 3 N/Ni interface owns a more thermoneutral value for H* absorption ability toward HER and optimized dehydrogenation process for HzOR.

Replacing the sluggish anode reaction in water electrolysis with thermodynamically favorable hydrazine oxidation could achieve energy-efficient H2 production, while the shortage of bifunctional catalysts limits its scale development. Here, we presented the scalable one-pot synthesis of partially exposed RuP2 nanoparticle–decorated carbon porous microsheets, which can act as the superior bifunctional catalyst outperforming Pt/C for both hydrazine oxidation reaction and hydrogen evolution reaction, where an ultralow working potential of −70 mV and an ultrasmall overpotential of 24 mV for 10 mA cm−2 can be achieved. The two-electrode electrolyzer can reach 10 mA cm−2 with a record-low cell voltage of 23 mV and an ultrahigh current density of 522 mA cm−2 at 1.0 V. The DFT calculations unravel the notability of partial exposure in the hybrid structure, as the exposed Ru atoms are the active sites for hydrazine dehydrogenation, while the C atoms exhibit a more thermoneutral value for H* adsorption.

The cobalt carbonate hydroxide nanowires (Co(CO3)0.5(OH)·0.11H2O, CCO NWs) have gained sufficient attention as promising catalyst, while its potential capability towards photocatalytic CO2 reduction (PCR) has not been excavated yet. Herein,...

Water electrolysis has been expected to assimilate the renewable yet intermediate energy‐derived electricity for green H2 production. However, current benchmark anodic catalysts of Ir/Ru‐based compounds suffer severely from poor dissolution resistance. Herein, an effective modification strategy is proposed by arming a sub‐nanometer RuO2 skin with abundant oxygen vacancies to the interconnected Ru clusters/carbon hybrid microsheet (denoted as Ru@V‐RuO2/C HMS), which can not only inherit the high hydrogen evolution reaction (HER) activity of the Ru, but more importantly, activate the superior activity toward the oxygen evolution reaction (OER) in both acid and alkaline conditions. Outstandingly, it can achieve an ultralow overpotential of 176/201 mV for OER and 46/6 mV for the HER to reach 10 mA cm−2 in acidic and alkaline solution, respectively. Inspiringly, the overall water splitting can be driven with an ultrasmall cell voltage of 1.467/1.437 V for 10 mA cm−2 in 0.5 m H2SO4/1.0 m KOH, respectively. Density functional theory calculations reveal that armoring the oxygen‐vacancy‐enriched RuO2 exoskeleton can cooperatively alter the interfacial electronic structure and make the adsorption behavior of hydrogen and oxygen intermediates much close to the ideal level, thus simultaneously speeding up the hydrogen evolution kinetics and decreasing the energy barrier of oxygen release.

Clean hydrogen evolution through electrochemical water splitting underpins various innovative approaches to the pursuit of sustainable energy conversion technologies,but it is blocked by the sluggish anodic oxygen evolution reaction (OER). The hydrazine oxidation reaction (HzOR) has been considered as one of the most promising substitute for OER to improve the efficiency of hydrogen evolution reaction (HER). Herein, we construct novel dual nanoislands on Ni/C hybrid nanosheet array:one kind of island represents the part of bare Ni particle surface,while the other stands for the part of coreshell Ni@C structure (denoted as Ni-C HNSA), in which exposed Ni atoms and Ni-decorated carbon shell perform as active sites for HzOR and HER respectively.Asaresult, when the current density reaches 10 mA cm À2 ,the working potentials are merely À37 mV for HER and -20 mV for HzOR. At woelectrode electrolyzer exhibits superb activity that only requires an ultrasmall cell voltage of 0.14 Vtoa chieve 50 mA cm À2 .